Heretofore, in a digital broadcasting system, as shown in FIG. 1, video data is compression-encoded in the MPEG (Moving Picture Experts Group) scheme with a video encoder 1, compression-encoded data ES is stored in an encoder FIFO2 and then transmitted to a decode buffer 3 of a decoding side as a transport stream TS. The decoder 4 reads out data which is stored in the decode buffer 3, at predetermined timing and decodes it.
In such a digital broadcasting system, approximately equivalent encoded data is transmitted to the decode buffer 3 every predetermined timing, thereby preventing the decode buffer 3 from overflow or underflow.
However, in the digital broadcasting system which transmits encoded data at a fixed rate, overflow or underflow occurs in a decode buffer if the transmission rate is variable for transmission.